1. Field of the Invention
The present invention relates to electrical plugs, and more particularly to a universal electrical plug adapted to the electrical sockets with different sizes.
2. Related Art
Referring to FIG. 1, an electrical plug 1 in the prior art is disposed at an end of a power output cable of an electric transformer or a power supplier. The electrical plug is utilized to be inserted a corresponding electrical socket to electrically connect the electric transformer or the power supplier to the electrical socket, therefore supplying power to the electronic device equipped with the electrical socket.
Referring to FIG. 2, the electrical plug 1 includes a base portion 2, an outer sleeve 3, an inner sleeve 4. The base portion 2 is made of electrical insulating medium, and an end of the outer sleeve 3 is connected to the base portion 2. The inner sleeve 4 is disposed inside the outer sleeve 3, and the outer sleeve 3 and the inner sleeve 4 are spaced by an insulating ring 5 to prevent the outer sleeve 3 and the inner sleeve 4 from contacting each other. The electrical plug 1 further includes two leads 6, 7, buried in the base portion 2. The lead 6 is electrically coupled to the outer sleeve 3 while the lead 7 is electrically coupled to the inner sleeve 4, so as to connect the outer sleeve 3 and the inner sleeve 4 to the power output cable of the electric transformer or the power supplier.
Referring to FIG. 2, the electrical socket 8 corresponding to the electrical plug 1 includes a body 9, a conductive pin 10, and a plurality of contact reeds 11. The body 9 includes an inserted hole 12, and the conductive pin 10 is disposed at the bottom end of the inserted hole 12 of the inserted hole 12 and extends outwards in a central axis of the inserted hole 12. The contact reeds 11 are embedded on an inner wall of the inserted hole 12, and part of or the whole contact reed 11 protrudes beyond the inner wall of the inserted hole 11.
The following conditions are required for the sizes of the electrical plug 1 and the electrical socket 8 to inserting the electrical plug 1 into the electrical socket 8 and electrically connect the electrical plug 1 into the electrical socket 8. Firstly, the outer diameter of the outer sleeve 3 has to be smaller than or equal to the internal diameter of the inserted hole 12, so as to insert the outer sleeve 3 into the inserted hole 12. Furthermore, the external diameter of the outer sleeve 3 has to be large enough for the contact reed 11 to contact and clamp the outer sleeve 3. Secondly, the internal diameter of the inner sleeve 4 has to be slightly large the external diameter of the conductive pin 10, so as to insert the conductive pin 10 into the inner sleeve 4 to have the conductive pin 10 contacting and electrically connecting to the inner sleeve 4.
Referring to FIG. 2, the geometry specification of the electrical plug 1 has to match that of the electrical socket 8. If the internal diameter of the inserted hole 12′ of an electrical socket 8′ is to smaller than the external diameter of the outer sleeve 3, the outer sleeve 3 of the electrical plug 1 can not be inserted into the inserted hole 12′. On the contrary, if the inserted hole 12′ of the electrical socket 8′ is too large, the outer sleeve 3 can be inserted into the inserted hole 12′. However, under such condition, the outer sleeve 3 may not continuously contact with the contact reeds 11′, or the outer sleeve 3 may not be fixed in the inserted hole 12′ by the contact reeds 11′. Similarly, if the external diameter of the conductive pin 10′ of the electrical socket 8′ is larger than the internal diameter of the inner sleeve 4, the conductive pin 10′ of the electrical plug 1 can not be inserted into the inner sleeve 4. On the contrary, if the external diameter of the conductive pin 10′ is too small, the conductive pin 10′ will not well contact with the inner sleeve 4 after the conductive pin 10 is inserted into the inner sleeve 4. According to the abovementioned reasons, every electric transformer or power supplier can only match one or a few types of electrical sockets 8 having matched geometry specifications. To electrical sockets 8, 8′ having different geometry specifications, manufacturers of electronic devices have to reserve large amount of the electrical plugs 1 having different geometry specifications even the electrical specification of each electric transformer or power supplier can match the requirement of various types of electronic devices.
To solve the aforementioned problems, a solution in the prior art is to utilize detachable electrical plugs in electrical transformers or power suppliers. Such kind of electrical plug can be detached from the end power cable and replaced by another electrical plug having suitable geometry specification. However, the abovementioned solution has another problem that the user may lost the detachable electrical plugs detached from the power cable. Therefore, the electrical transformer or the power supplier may not be used any more if the frequently used detachable electrical plug is lost.